Artificial sweeteners trick flies into thinking they’re starving

Whether artificial sweeteners are helpful or harmful for weight loss has long been argued. A new study on flies provides more evidence for the latter, indicating that sweeteners might confuse your brain into wanting more food than it needs.

Why it matters:

Numerous studies in animals have linked weight gain with artificial sweeteners. And some human research has suggested artificial sweeteners may increase a person’s risk of metabolic problems. One recent study suggested that the cause of such metabolic changes could be a change in the gut microbiome. But the health consequences of artificial sweeteners remain controversial, and the mechanisms that could explain these effects are still uncertain.

The nitty gritty:

Researchers studied fruit flies who could eat their fill of either a normal diet or one with supplemental sucralose, the artificial sweetener marketed as Splenda. After a few days, the flies on the sucralose diet were eating up to 30 percent more calories than the other flies.

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When scientists then fed both groups normal sugar and looked at the flies’ brain activity, they found that flies fed sucralose showed much more neuron firing in response to normal sugar, suggesting the flies found that sugar to be sweeter as a result of their diet.

When the team replicated the study in mice, they found the same brain patterns, indicating that a similar mechanism might be at play in people. The research was published in Cell Metabolism Tuesday.

You should know:

The neural pathways involved are also those that make food taste better when you’re starving, said Gregory Neely, a functional geneticist at the University of Sydney in Australia and one of the study’s senior authors.

“What the sucralose is doing is making them think that they need to eat even though they don’t,” said Purdue neuroscientist Susan Swithers, who was not involved with the study. “People ask, ‘How could something without any calories produce negative outcomes?’ and this is providing evidence for how that could happen,” Swithers said.

But the study didn’t find any involvement of the microbiome. Flies whose microbiomes were controlled with antibiotics or through limited exposure to microbes still showed increased appetite when consuming sucralose. Neely said one possible explanation for the difference could be that the earlier study that showed sweeteners may alter the microbiome was conducted on mice and humans, not flies.

But keep in mind:

Flies don’t perceive sucralose to be as sweet as humans do, said Neely, meaning the dose given to flies was much higher than would have been ideal for mimicking human circumstances.

And sucralose is just one kind of artificial sweetener. It’s possible that others with different molecular structures might affect the brain differently.

The bottom line:

Our brains compare calories and sweetness to calculate how much we should eat, and artificial sweeteners may confound that math and cause us to eat more calories as a result.

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